Film quenching apparatus



Aug. 10, 1965 H. P. KOPPEHELE FILM QUENCHING APPARATUS Filed April 20. 1962 United States Patent linge Paul l"- enschede7 G A* sun Corporation, ifilila @elan/ar Apr. 29, 1962,

The present invention relates to the manufacture of sheet or films from iopiastic tilm-forrning materials, and more particularly' to an apparatus for quenching of a continuous shaped stream or sheet of nlm-fori .ing material without distorting the same.

In a conventional procedure for forming sheets or ilms, as for example from polypropylene or polyethylene, molten -lorrning material is extruded as a continuous shaped stream or si of substantially uniform thickness and then quenched within a bath of cool water or other suitable liquid. The quenched sheet is dried and then oriented by being stretched along one or both of its axes while in a heated condition, to improve the physical and perhaps the optical properties thereof. It has been found, however, that dui ug the quenching stage variations are nai* von.

induced or thickness ot the sheet along its length. areas of different thickness do not respond e r' the subsequent heating and stretcha operation, the stretched sheet exhibits gage variations witch are now magnilied. Further, in view of the difterential molecular orientation etected during the stretching operation, the resulting sheet possesses non-uniform physical and/or optical properties.

TlJarious proposals have been made for eliminating or at least mini ing the above described problem. Such proposals g ierallv involve the use of batlles, selds and dedectors as well as specifically designed jets or manifolds for controlling the direction and movement of th cooling liquid. None of these prop-osais, however, have proven to be satisfactory. Accordingly, a primary object of this invention is to provide a new or generally improved and more satisfactory apparatus for quenching ot shaped streams or sheets of molten film-forming material,

A `further object is the provision of an improved appary 'us for quenching an ex eed stream or" molten illint'orming material by subiecting the opposite sides thereof to high volume, lov.7 velocity flows of cooling liquid.

A still further obliect is the provision of an improved anmratus in which opposite sides of a continuous shaped s* earn of molten hlm-forming material are quenched by high volume, lou' velocity streams of cooling liquid maintained at substantially the same temperature.

These and other objects adv ages of the invention will be apparent Wein the following description and accompanying drawing in which:

FIGURE l is a plan view of a nortion of the quenchapparatus of the present invention; and

2 is a vertical section taken longitudinally the structure shown in l.

The prevent invention is bas d upon my discovery that vai ations induced a: z1` the length of a shaped stream of molten flln -or i aterial during the quenching thereinc are due primarily to: (l) changes in the melt draw-down ratio of the extruded film-forming material, and changes the melt draw distance, or in other words, ch .nges in the length of that portion of the eX- truded stream of n-iorming material which is subjected to a drawing action.

The melt draw-down ratio can be best denne-d as the ratio of the take-olf sneed or the speed at which the quenched sheet is withdrawn from the quench bath to the velocity et the molten 'film-forming material Ias it issues from an extrusion nczzl Change in the melt drawdown ratio can be mi imi-2cd by employing take-up rolls ice which are capable of removing the quenched sheet from the quench bath at a predetermined metered rate of speed and/or by using an extrusion apparatus which provides for a substantially uniform delivery of film-forming material to the extrusion nozzle. The present invention is therefore particularly concerned with the problem of eliminating or minimizing changes in the melt draw-down distance.

The melt draw distance is dened as the distance from the extrusion nozzle to the point below the surface of the quench bath at which the shaped stream of nlm-forming material solidies. This point at which solidification of the shaped stream or sheet of film-forming rst occurs is generally visible as a frost line which extends across the sheet. The location of the frost line is dependent upon such factors as the temperature and specific heat of ti-e particular film-forming material employed, the distance between the extrusion nozzle and the surface of the quench bath, the temperature of the quenching or cooling liquid, and the gage of the sheet or film which is being formed. Basically, the present invention is directed to an ap aratus in which the distance between the extrusion nozzle and the surface of the quench bath and the ternpcrature of the quenching liquid are maintained substantially constant throughout the film-forming operation.

ln accordance with the method practiced with the apparatus of the present invention, a shaped stream or sheet of molten {ihn-forming material is quenched by high volume, low velocity streams of cooling liquid which sweep the opposite sides of the shaped sheet of hlm-forming material, and in a direction opposite to the movement of such sheet, and are then discharged. In this manner localized heating of the quenching liquid is avoided so that successive portions of the shaped stream or sheet of hlm-forming material are quenched by cooling liquid which is at substantially a constant temperature. With continued advancement of the quenched sheet, its opposite sides are swept by high volume, high velocity streams of cooling liquid which provide for a more ellcient quenching action of the sheet throughout its thickness. Subsequently, the quenched sheet is withdrawn trom the quench bath at a metered rate of speed, during which movement, its opposite surfaces are again subg'ected to high volume, low velocity streams of cooling liquid. As more fully described hereafter, the surface area of the quench bath employed in the present method is maintained at a minimum to prevent any build-up of waves or other surface luctuations as the shaped sheet of {ihn-forming material enters and leaves the quench bath.

The apparatus for practicing the above described method includes a quench tanlr Ifor containing a cooling liquid, a nozzle for extruding a uniform shaped stream or sheet of nlm-forming material into the quench tank and rolls for removing the quenched sheet from the tank at a metered rale ot sneed. Within the area below the metering rolls, the quench tank includes means for directing a high volume, low velocity tlow of cooling liquid against opposite sides of the sheet. This cooling liquid ilows in `a direction opposite to the travel of the sheet and is withdrawn from opposite sides thereof, as high volume, low velocity streams, in the area of the tank below the extrusion nozzle,

The apparatus of the present invention is adapted for use with thermoplastic, polymeric nlm-forming materials which may be shaped into a desired lilm or sheet by melt casting procedures. Further, the sheets or films produced in accordance with the present invention may be of uniiorm or varying cross-section or may be provided with thickened or beaded portions along its opposite longitudinal edges.

With reference to the drawing, the apparatus of the present invention includes a nozzle or die 5 for extruding a shaped stream or sheet 7 of molten film-forming material, a quench tank 9 for containing a cooling liquid il, such aswater, for quenching the shaped stream of filmforming material into a solid sheet or film 13, and a pair of nip rolls for withdrawing the sheet 13 from the quench tank9 at a uniform rate of speed.

The tank 9 may be of any desired configuration and, as illustrate-d, includes a bottom wall 17, side walls i9 and end walls 21. Positioned within the tank 9 and directly below the nip rolls l5 are a pair of spaced chambers or conduits 23 and 25, of which opposing walls 27 and 29 are perforated as shown at 3l. Cooling liquid 1l is delivered into the chambers 23 and 25 by pipes 33 which are in turn connected to a suitable supply source, not shown.

rthe opposite end of the tank 9 is similar to that described above and includes a pair of spaced chambers or conduits 35 and 37 positioned below the nozzle 5 and having opposed walls 39 and 41 perforated, as shown at 43. Pipes 45 are disposed Within the chambers 35 and 37 and are connected to a common discharge conduit 47 whereby cooling liquid fill withdrawn through chambers 35 and 37 may be refrigerated and returned to the quench tank 9 through chambers 23 and 25.

As illustrated the chambers and 37 terminate above the bottom wall 17 of the tank 9. A divider or partition 49 extends between the lower ends of these chambers 25 and 37 and includes an access door 5l. and door l-ock 5.3. Rolls 55 are positioned adjacent to Vthe bottom wall of the tank 9, generally in alignment with `the spaces between cooperating pairs `of chambers, for guiding the sheet i3 along a desired path through the quench tank.

In use, cooling liquid lll is delivered through pipes 33 and the perforated walls of chambers 23 and 25 t0 substantially ltill the tank 9, including the portion thereof located above the divider 49. Molten film-forming material is then extruded from the nozzle 5 as a shaped stream 7 which travels downwardly into the quench tank 9 in-between the chambers 35 and 37. As the stream 7 enters the cooling liquid, at least its surfaces are rapidly set or quenched to provide the continuous sheet or iilm 13. By opening the access door 5l, the sheet 13 may be readily laced around the rolls 55 and then upwardly in-between the chambers 23 and 25 tothe metering rolls l5. The access door 51 is then locked in its closed position afterwhich the cooling liquid above the divider 49 may be re- Vmoved by any conventional pump means.

' With the apparatus laced as described above, cooling liquid 1l is continuously delivered into the chambers 23 and 25 and fiows therefrom through the .perforations 31. As indicated by arrows 57 the cooling liquid 11 hows along opposite sides of and in a direction counter to thatY of the quenched sheet 13. Between the chambers 35 and 37, the cooling liquid il sweeps along the opposite sides of the shaped stream of film-forming material as it initially enters the quenching tank and is then discharged through the chamber perforations 43 and pipes 45.

It will tbe apparent Athat .as the cooling liquid sweeps along the opposite side of the shaped stream of film-forming material, heat is extracted therefrom to at least set the surface portions thereof into the form of sheet 13. Further, following this sweeping movement along the sheet 7, the cooling liquid is continuously discharged into the chambers 35 and 37. As a result, the successive portions of the shaped-stream of film-forming material are solidified at substantially the same point within the quench tank; that is, the distance between the extrusion nozzle and the frost line across the sheet or film 13 remains constant throughout the method.

The number, size, and arrangement of the perforations p Si and 43 formed in the opposing walls of the respective pairs of chambers may be varied to suit particular operating conditions. The perforations 31 formed in the opposed chamber walis 27 and 29V preferably provide for a high volume, low velocity flow of equal amounts of cooling liquid 11 to the opposite sides of the sheet of iilm 13. Similarly, the perforations 43 in the opposed chamber walis 39 and il must facilitate a high volume, low velocity flow of liquid il away from `opposite side of the sheet after it has performed its quenching function.

While the perforations Si preferably define a total open area which is substantially equal to that provided by the perforations d3, such open area should be greater than the cross sectional area of passageway 5? which is formed by the bottom wall l, thedivider 49 and the ad- Y jacent portions of the tank side walls i9. With this arrangement, a comparatively high volume, high velocity iiow ofcooling liquid` ll is provided within the passageway Since this flow runs counter to the direction of travel of the sheet i3, any liquid carried by and along with sheet 13 is swept clear of Vthe opposite surfaces to thus provide for a more uniform, rapid and efficient quenching action.

it will be noted that with the delivery of cooling liquid as described above, bubbles or air or other gases contained therein are well removed from the area in which the moiten stream of film-forming material rst enters the quench tank and therefore are not able to mar or otherwise effect the surfaces thereof.

Aside from satisfying easy lacing operations, the spacing between the cooperating chambers of each pair of chambers should be kept to a minimum. In this manner, the small si rface areas of the cooling liquid at the entrance and exit portions of the quench tank minimize any build-up of surface waves or other fluctuations.

As illustrated, the chambers 23 and 35 are substantially equal in height to the chambers 25 and 37. If desired, the lower portions of the chamber walls 27 may be perforated, as indicated by broken lines, to permit additional cooling liquid to be delivered into the passageway 59 and subsequently discharged through similar perforations formed in the lower portion of the chamber wall 39.

It is to be understood that changes and variations may be made without departing from the spirit and scope of the invention as defined in the appended claims.

I claim: Y

l. Apparatus for use in the manufacture of films including a tank having a bottom wail and upright side and end walls, a pair of spaced upright, perforated partitions disposed adjacent to each of said end walls and eX- tending between the side walls thereof, the lower ends of adjacent partitions of said pairs of partitions terminating above the bottom wall of said tank, a divider plate eX- tending between the lower ends of said adjacent partitions and the side walls of said tank, means for deliverin; a cooling liquid through the perforations of one pair ef'said partitions, means for withdrawing cooling liquid through the perforations of the other of said pair of partitions, means for extruding a sheet ofV molten filmforming material into the cooling liquid irl-between the partitions Vof said other pair of partitions, means for withdrawing the cooled sheet of film-forming material from the cooling` liquid between the partition of said one pair of partitions, and means for directing the cooled sheet of film-forming materiai between the bottom wall of said tank and said divider as the sheet is advanced in a direction counter tothe flow of cooling liquid.

2. In an apparatus for use in the manufacture of continuous films, a tank having a bottom wall and upright side and end walls, a first pair of spaced chambers extending between the side walls of said tank adjacent to one end wall thereof, a second pair of spaced chambers extending between the side walls of said tank adjacent to the opposite end wall thereof the lower ends of adjacent chambers of said rst and second pairs of chambers terminating above the bottom wall of said tank, a par-tition extending between said lower ends of said adjacent chambers and cooperating with the bottom and side walls snaai/ie of said tank to form a passageway which provides a continuous passage between said iirst and second pairs of chambers, opposing walls of each pair of said chambers having similar perforations, means for delivering a cooling liquid through the perforated walls of said first pair of chambers and into the space therebetween, and means for withdrawing cooling liquid from the space between said second pair of chambers through the perforated walls thereof.

3, Apparatus as defined in claim Z wherein the perforated areas of said irst and second pairs of chambers are substantially equal but greater than the cross sectional area of said passageway,

4. Apparatus as deined in claim 2 further including means for delivering a shaped sheet of molten hlm-forming material between said second pair of chambers and into the cooling liquid to quench the same, means for withdrawing the quenched sheet of film-forming material from the cooling liquid between said iirst pair of chambers, and means within Said tank for directing the quenched sheet along said passageway.

5. Apparatus as defined in claim 4 further including a door in said partition for use in lacing the sheet through said passageway.

6. Apparatus for use in the manufacture of films including a tank having a bottom wall and upright side and end walls, a pair of conduits disposed adjacent to each of said end walls and extending between the side walls of said tank, the conduits of each pair ol' conduits being spaced from each other, means for delivering a liquid to one pair of said conduits, a plurality of openings formed in opposing surfaces of said one pair of conduits for discharging liquid therefrom and into the space between such conduits, a passageway for directing the liquid from the space between said one pair of conduits to the space between the other of said pair of conduits, a plurality of openings formed :in opposing surfaces of said other pair of conduits for withdrawing liquid from the space therebetween, means for removing liquid from said other pair of conduits, the surface area included by the openings in each pairs of conduits being substantially equal, means for extruding a shaped stream of filmiorming material into the space between said other pair of conduits and thereby' solidify the same into a film by the liquid contained therein, and means for withdrawing the film from the space between the said one pair of conduits.

7. Apparatus as defined in claim 6 wherein the surface area included by the openings of each pair of conduits is greater than the cross-sectional area of said passageway.

References Cited by the Examiner UNITED STATES PATENTS 1,748,868 2/30 Dethlof 18-15 2,077,836 4/37 Herndon 18-15 2,210,116 8/40 Dreyfus 264-180 2,264,357 12/41 Bleibler 18-15 2,494,468 1/50 Borzylrowski 264-188 X 2,627,684 2/53 Ryan 188 2,923,979 2/60 Kalil 18-57 2,957,206 .l0/60 Mindick et al 18-57 2,987,373 6/61 Benzemer et al 264-178 FOREEGN PATENTS 412,691 7/34 Great Britain.

WILLAM I. STEPHENSON, Primary Examiner.

MORRS LEBMAN, MCHAEL V. BRINDSI,

Examiners. 

1. APPARATUS FOR USE IN THE MANUFACTURE OF FILMS INCLUDING A TANK HAVING A BOTTOM WALL AND UPRIGHT SIDE AND END WALLS, A PAIR OF SPACED UPRIGHT, PERFORATED PARTITIONS DISPOSED ADJACENT TO EACH OF SAID END WALLS AND EXTENDING BETWEEN THE SIDE WALLS THEREOF, THE LOWER ENDS OF ADJACENT PARTITIONS OF SAID PAIRS OF PARTITIONS TERMINATING ABOVE THE BOTTOM WALL OF SAID TANK, A DIVIDER PLATE EXTENDING BETWEEN THE LOWER ENDS OF SAID ADJACENT PARTITIONS AND THE SIDE WALLS OF SAID TANK, MEANS FOR DELIVERING A COOLING LIQUID THROUGH THE PERFORATIONS OF ONE PAIR OF SAID PARTITIONS, MEANS FOR WITHDRAWING COOLING LIQUID THROUGH THE PERFORATIONS OF THE OTHER OF SAID PAIR OF PARTITIONS, MENS FOR EXTRUDING A SHEET OF MOLTEN FILMFORMING MATERIAL INTO THE COOLING LIQUID IN-BETWEEN THE PARTITIONS OF SAID OTHER PAIR OF PARTITIONS, MEANS FOR WITHDRAWING THE COOLED SHEET OF FILM-FORMING MATERIAL FROM THE COOLING LIQUID BETWEEN THE PARTITION OF SAID ONE PAIR OF PARTITIONS, AND MEANS FOR DIRECTING THE COOLED SHEET OF FILM-FORMING MATERIAL BETWEEN THE BOTTOM WALL OF SAID TANK AND SAID DIVIDER AS THE SHEET IS ADVANCED IN A DIRECTION COUNTER TO THE FLOW OF COOLING LIQUID. 